Solution:

F

Explanation: The letters are the first letter of each of the twelve months. The second month is February.

Solution:

It can be solved as below.

Solution:

C7 => B8
Exchange pawn for a knight

Check-Mate

GameOver

Solution:

19

Explanation:
The children can purchase 19 chocolates in return.

Out of 77 wrappers, 75 will be used to buy 15 chocolates and two will be left spare.
The 15 chocolates will create 15 empty wrappers that can be exchanged to get three chocolates.
Three chocolates will return three wrappers which will help them buy another chocolate.
Now the wrapper from this chocolate and the two spare that were left earlier will get them another chocolate.
15 + 3 + 1 = 19

Solution:

Michelangelo juggles the diamonds across while crossing the bridge.

Solution:

The man asked the king that he wanted to die of old age.

Solution:

On the back, since bullet train is accelerating, therefore,the person at the back will spend less time than one in front.

Solution:

Colors:
Y B R G
G R B Y
B Y G R
R G Y B


Signs:
x + - /
- / x +
/ - + x
+ x / -

Solution:

Yes it is possible in Roman Numerals. In Roman Numerals,
9 = IX
10 = X
11 = XI

Thus by removing one from 9, you are getting 10 and by removing one from 11, you are getting 10 again.

Solution:

One Minute building

building 62 => Sixty second building => One minute building

Solution:

It can be done as shown in the picture below.